textproduct: Rapid City

KEY MESSAGES

- Critical fire weather conditions over parts of northeastern Wyoming and extreme southwestern South Dakota late Monday morning through early Monday evening

- Above average temperatures remain in the start of the forecast. Afternoon temps will be in the upper 80s to 90s for Monday but cooler temps expected midweek.

- Elevated to potentially critical fire weather conditions linger for much of next week

- Isolated to scattered thunderstorms are expected through Monday morning.

UPDATE

Issued at 948 PM MDT Sun Sep 6 2026

03z surface analysis had low over southeast MT with a warm front into southern ND and a trough into ID. Water vapour loop had deep southwest flow from the southwest CONUS into the northern Plains. Several impulses wiggling along the edge of a 130kt jet. Next impulse traveling through eastern WY, assisting convection as a forecast 20-35kt low level jet develops ahead of surface low. Starting to see evidence of that per regional radar loop and KUDX VWP. Isolated/scattered TSRA will move northeast through the CWA overnight into Monday morning with general CAM agreement.

Surface low will deepen Monday as upper trough translates eastward. Cold front trailing low will invade the CWA late with deep southwest boundary layer mixing ahead of it over northeastern WY/southwestern SD. Expect very dry to develop ahead of the cold front with gusty west/southwest winds. Combination will create critical fire weather conditions, so have issued a Red Flag Warning to account.

Rest of forecast in decent shape for now with a somewhat cooler temperatures making an appearance for a couple of days next week.

DISCUSSION

(This Evening Through Sunday) Issued at 1202 PM MDT Sun Sep 6 2026

A change in the winds is coming to the area this week. The last couple of days, we have been under the influence of a large upper level ridge that has been giving us southwest flow in the higher parts of the atmosphere. Through tomorrow, an upper level low spinning over the pacific northwest will kick eastward. This low will shift upper level winds over the CWA from the southwest to west. This means passing storm chances, then slightly cooler temps. And the longer term forecast is hinting at bigger swings in temps that could mean bigger breaks from the heat.

At the surface, an area of low pressure will develop near north central Wyoming later today. This low is expected to track northeast tonight through tomorrow. And as it moves east tomorrow, north of the CWA, it will swing a cold front through the area.

Showers and thunderstorms are likely as these changes happen through tomorrow. For today, storms are expected to pop up over the Black Hills during the heat of the day and these storms will move east-to-northeast through the afternoon and evening. At the same time, more storms are likely to develop to our south and those will drift northwards later this evening and overnight. Severe weather can't be ruled out with hail and strong winds being the main concerns. The SPC has placed a Marginal risk centered over the Black Hills and the surrounding plains. Machine learning severe weather models are also highlighting the same area.

Late tonight into early Monday, the previously mentioned cold front will slide west to east over the area. pushing any lingering precip, or new rain/storm development, eastward. Based on current projections though, the bulk of any rain and showers tomorrow will be gone by midday with mostly sunny to partly cloudy skies Monday afternoon. The rest of the week looks dry with the next round of rain possible next weekend. Once the front pushes through, westerly winds will pick up some speed. Monday afternoon winds will be strongest in NE WY at upwards of 20 to 25 mph, gusts over 30 mph. Then Tuesday, the strongest winds will shift to the NW SD plains at around 20 to 30 mph, gusts nearing 40 mph.

Lastly, the temperature outlook for this week has some big swings. Afternoon highs take a dip after today and tomorrow's highs in the upper 80s to 90s with Tuesday and Wednesday's highs in the 70s to 80s. Highs in the 80s and 90s return Thursday and Friday. Next weekend could see temps below normal, stay tuned.

AVIATION

(For the 00Z TAFS Through 00Z Monday Evening) Issued At 519 PM MDT Sun Sep 6 2026

Isolated/scattered thunderstorms will slowly move northeast across portions of northeastern WY/western SD tonight, waning from southwest to northeast Monday. Local MVFR conditions may occur with any thunderstorm along with gusty, erratic winds. Low confidence terminals will be affected, so left out of forecast for now. Outside of thunderstorms, VFR conditions are expected with gusty southerly winds, especially on the open plains.

FIRE WEATHER

Issued At 1202 PM MDT Sun Sep 6 2026

Fire weather continues to be a concern with elevated to near critical conditions likely. Afternoon temperatures in the 80s to 90s to start the week. And very dry weather lingers with minimum relative humidity down to 10 to 20 percent for the western zones. And once a cold front pushes through, westerly winds will pick up with gusts upwards of 25 to 40 mph at times for Monday and Tuesday. Lighter winds expected for the second half of the week.

UNR WATCHES/WARNINGS/ADVISORIES

SD...Red Flag Warning from 11 AM to 7 PM MDT Monday for SDZ322. WY...Red Flag Warning from 11 AM to 7 PM MDT Monday for WYZ314>317.